1. Field of the Invention
This invention relates to a passive-motion orthopedic seat, and more particularly, to a passive-motion orthopedic seat having a support surface adapted to be continuously reconfigured, thereby causing a person seated on the support surface to continuously and instinctively adjust the attitude of his spinal column and associated muscles.
2. Related Prior Art
Many occupations require the worker to remain in virtually the same seated position or attitude for prolonged periods. While this has always been so in the case of sedentary workers confined to a fixed work station, the number of such workers has increased enormously in the modern era with the rapid evolution of technology and the concomitant institution of highly efficient systems of production of both goods and services. The computer terminal and the personal computer, now ubiquitous in private life and home employment as well as in the traditional workplace, are notorious for anchoring their users in a chair for hours at a time, confronting a keyboard in an upright posture. Without realizing it, such a user tends to maintain one posture rigidly for long periods without adjusting the attitude of his spinal column and associated muscles.
It is therefore hardly surprising that such workers, and hobbyists as well in many instances, increasingly complain of back pain of varying degrees of frequency and intensity, some of it so severe as to be disabling. Although a great variety of adjustable chairs have been devised to enhance the comfort of such persons, the chairs are usually adjustable only with regard to the height or angle of the seat and the angle of the backrest and do not address the problems created by rigidly maintaining the same seated attitude for extended periods.
Exercises are often prescribed as therapy by medical professionals for the relief or correction of back conditions, chronic or temporary, but their patients or clients tend to neglect to perform such exercises regularly because of the physical effort and concentration required. There is therefore a need for a passive exerciser, ideally a passive-motion orthopedic seat, which may be employed by the patient or client to realize the benefits of the therapy without consciously exerting noticeable physical effort and while carrying out some other activity.
Various expedients have been proposed for automatically moving bodily parts between positions or attitudes. For example, in U.S. Pat. No. 5,197,461, issued Mar. 30, 1993 to J. H. Petajan et al., there are described and illustrated a series of orthopedic pillows, each of which is specifically configured to receive and conform to a particular, individual bodily limb or extremity. When the limb or extremity is placed to rest upon it, the pillow is cyclically inflated and deflated by means of a pump to cause the limb or extremity to be repeatedly raised and lowered for therapeutic purposes. The cycle of inflation and deflation is governed, not by time-actuated means, but by a pressure-sensitive switch. Clearly, the patient undergoing such therapy is expected to be entirely passive and relaxed throughout the treatment. The Petajan patent is representative of a body of such art, which also includes U.S. Pat. No. 3,477,071, issued Nov. 11, 1969 to J. H. Emerson, and U.S. Pat. No. 3,492,988, issued Feb. 3, 1970 to B. L. De Mare.
U.S. Pat. No. 5,022,385 issued Jun. 11, 1991 to R. D. Harza, is directed to a method and a device for periodically and rhythmically raising first one hip of a seated person and then the other to simulate the muscle stimulation and relaxation which would be imparted through walking. More particularly, Harza provides a seat section which is limited to only two inflatable cells, one to be positioned directly under the left hip of the seated person and the other to be positioned directly under the right hip. To achieve the simulated walking motion, Harza inflates and deflates the two cells alternately.
U.S. Pat. No. 3,270,440, issued Sept. 6, 1966 to T. Radosevic, Jr., discloses a seat having a bottom cushion formed of three independently inflatable cells of equal size and shape and aligned in a row from right to left. However, the Radosevic, Jr. patent is directed to a flight simulator, and thus the internal pressure in each of the cells is variously increased and decreased, not according to a predetermined program, but directly in response to a seated person's manipulation of controls similar to those provided in aircraft, whereby to simulate the feeling of the motions which result from performance of various aircraft maneuvers.
U.S. Pat. No. 4,840,425, issued Jun. 20, 1989 to R. H. Noble, discloses a seating assembly comprising alternating sets of elongated inflatable compartments that extend across a seat and backrest, each set independently supporting a seated person when pressurized to a degree greater than the other set. A control mechanism acts to alternately inflate and partially deflate each set, with inflation occurring from the rear of the seat portion forwardly and from the bottom of the backrest upwardly.
A somewhat similar device is disclosed in U.S. Pat. No. 3,867,732, issued Feb. 25, 1975 to W. C. Morrell, and another, directed specifically to therapeutic massage, is disclosed in U.S. Pat. No. 3,613,671, issued Oct. 19, 1971 to J. H. Poor et al.